Sludge filter for separating sludge liquids from sludge solids

ABSTRACT

A sludge filter is comprised of a mesh filter media secured to a support net. The support net includes a front surface adjacent the filter media and a rear surface opposite the filter media, the rear surface having a plurality of outwardly extending nodes to define flow channels for horizontal and vertical fluid flow intermediate the net and a container surface. The sludge filter is attached directly to the walls or floor of a container. In a preferred embodiment a border of the sludge filter comprises one part of a two-part fastener system with a second part of the two-part fastener system attached to a container along the perimeter of the filter coverage area, so that the filter medium may be removably attached to the container.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/376,352, entitled “Filter for Sludge Filtration,” filed Feb. 27,2003, now U.S. Pat. No. 7,179,377.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to sludge filtration systems forseparating sludge solids from sludge liquids. More specifically, thisinvention relates to a filter for use in a container, designed forsludge filtration.

2. Description of the Related Art

The separation of sludge solids from sludge liquid is commonly practicedas an initial step in disposing of waste sludge. Generally, sludgeincludes, among other things, solid-liquid sludge and slurries such assewage and industrial waste.

When treating sludge, it is desirable to separate the sludge liquidsfrom the sludge solids for further treatment or recovery or disposal ofthe solids and liquids separately. A typical filtering system involves acontainer having filter systems arranged around the container walls andthe container floor. Such systems commonly involve a metal, plastic,polypropylene or vinyl liquid-permeable filter mesh with openings suchthat particulates above a predetermined size do not pass through thefilter. Due to the weight of sludge, such filtering systems include asupport structure for the filter. The support structure is oftencomprised of a perforated plate or expanded metal plate. The filtermedia may be attached to the support structure by retention bars. Anopening is typically provided intermediate the support structure and thecontainer wall to provide for drainage of the sludge liquids. Due to theexpense of disposable filters, it is desirable that the filter media berelatively strong.

Due to clogging effects of sludge containing small particulates, it isdesirable that the filter media be removable for cleaning orreplacement. As a result, prior art systems commonly use retainer barsto hold the filters and perforated plate in place. The retainer bars aretypically bolted to the support structure. Removal of the filters forwashing involves removing the retainer bars. Replacement of the filtersinvolves aligning openings in the filters, perforated plate and supportstructure. For a large sludge container, such as a commonly practicedroll on roll off container, the weight of the plate and filtersincreases the difficulty of removal and replacement.

In a typical prior art sludge-dewatering container, the combined widthof a support structure and filter is in the range of three inches (˜7.5cm) to six inches (˜15 cm). Such prior art filters extend within thecontainer and reduce the volume of sludge that can be processed by thecontainer.

This Applicant's U.S. Pat. No. 5,681,460 teaches a selectively removablesludge filtration system that provides for retrofit into a container andseparation of the sludge solids from the sludge liquids therein. ThisApplicant's U.S. Pat. No. 6,146,528 teaches removable filter assembliesfor containers that enable thorough and efficient cleaning of the filtersystem. U.S. Pat. Nos. 4,929,353 and 5,589,081, issued to Harris,disclose basket-like filter structures. U.S. Pat. No. 4,929,353 teachesa filter that is placed in an existing structure, and is held in placewith the weight of the sludge independent any fastening system. U.S.Pat. No. 5,589,081 teaches a removable filter that relies on thehydrostatic pressure created by the mass of sludge to force positiveflow of sludge liquids out the drains found in the collection container.

Multiple layer structures for filtering are known in the art. Suchfilters often comprise a filter media with a support backing to providelateral rigidity to the filter media. U.S. Pat. No. 5,776,567 toSchilling, et al. teaches a disposable multi-layer filter for separatingsolid and liquid wastes. U.S. Pat. No. 5,098,364 to Schilling, U.S. Pat.No. 5,110,005 to Schilling, U.S. Pat. No. 5,741,208 to Moak and U.S.Pat. No. 4,385,953 to Beck each teach liners for waste containers. U.S.Pat. No. 5,131,709 to Spica teaches a cargo bed liner system utilizing aplurality of grid-like modules.

It would be an improvement to the art to provide a re-usable sludgefilter that does not require a perforated plate, expanded metal or likesupport structure and that optimizes use of the interior space of acontainer for sludge filtration.

BRIEF SUMMARY OF THE INVENTION

Accordingly, the objects of my invention is to provide, inter alia, asludge filtration system that:

-   -   minimizes interior container space required for the filter;    -   is attachable to the interior surface of a container;    -   is removable for periodic cleaning;    -   can be adapted to suit various container shapes and sizes; and    -   may be readily removed and replaced.

Other objects of my invention will become evident throughout the readingof this application.

To fulfill such objectives, my invention is a sludge filter comprised ofa mesh filter media secured to a support net. The support net includes afront surface adjacent the filter media and a textured rear surfaceopposite the filter media. The sludge filter is attached directly to thewalls or floor of a container. In a preferred embodiment a border of thesludge filter comprises one part of a two-part fastener system with asecond part of the two-part fastener system attached to a containeralong the perimeter of the filter coverage area, so that the filtermedium may be removably attached to a container.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially cut-away side view of an embodiment of the presentsystem.

FIG. 2 is a perspective top view of the container of FIG. 1.

FIG. 3 is a cross-sectional view of the sludge filter.

FIG. 4 is a perspective view of a support net.

FIG. 5 is a cross-sectional view of the sludge filter disposed in atypical rectangular container.

FIG. 6 is a cross-sectional view of the sludge filter disposed in acontainer and including a vertical center filter panel.

FIG. 7 is a cross-sectional view of the sludge filter disposed in atypical rectangular container.

DESCRIPTION OF THE INVENTION

Referring to FIGS. 1 and 2, a sludge filter 10 of the present inventionis depicted installed in a typical sludge container 30. Referring toFIGS. 1 and 2, a typical container 30 includes a container floor 32,opposed sidewalls 31, a rear wall 36, and a front wall 38. The containerfloor 32, sidewalls 32, rear wall 36 and front wall 38 are sometimesreferred to herein as container 30 surfaces. The top 34 is typicallyopen to receive sludge. A cover, not shown, may be provided.

Referring to FIG. 3, in a cross-sectional view of the sludge filter 10,the sludge filter 10 comprises a filter media 24 and a net 26. In apreferred embodiment, filter media 24 comprises a planar mesh havingmultiple water-permeable openings extending transversely through themedia 24. A preferred material of filter media 24 is a pliablepolypropylene, nylon, polyester or wire mesh material.

The openings in filter media 24 may be determined in relation to themaximum size of particulate matter that is acceptable to pass throughthe filter media 24.

Referring to FIG. 4, net 26 comprises a generally planar material. Net26 has perforations 42 transversely through the net 26. The perforations42 of net 26 are relatively large in comparison to the openings (notshown) of media 24 as net 26 is intended as a support and spacingstructure and not as a filtering medium. Net 26 material comprises arelatively rigid material having some flexibility such as polypropylene,nylon, polyester or metal. The net 26 material resists compression inthe transverse direction yet is bendable along the plane of thematerial.

Referring to FIG. 3, net 26 has a front surface 77 and a rear surface79. In the preferred embodiment, rear surface 79 has a pattern ofindented sections 74 and extended nodes 76 relative to the plane of thenet 26. Front surface 77 may include a pattern of indented sections 70and extended nodes 72 relative to the plane of the net 26. For purposesof the sludge filter 10, it is necessary that the rear surface 79include indented sections 74 and extended nodes 76 to allow flow offiltered sludge liquids between rear surface 79 and container wallsurface inner surface 37.

The nodes 76 and indented sections 74 of net rear surface 79 create flowchannels 64 intermediate rear surface 79 and wall surface 37. As thenodes 76 and indented sections 74 extend laterally as well asvertically, the nodes 76 and indented sections 74 create multiple,interconnected fluid flow channels 64 intermediate rear surface 79 andwall surface 37, such fluid flow channels 64 allowing liquid flowhorizontally and vertically.

The nodes 72 and indented sections 70 of net front surface 77 createflow channels 62 intermediate front surface 77 and filter media 24. Asthe nodes 72 and indented sections 70 extend laterally as well asvertically, the nodes 72 and indented sections 70 create multiple,interconnected fluid flow channels 62 intermediate front surface 77 andfilter media 24, such fluid flow channels 62 allowing liquid flowhorizontally and vertically.

Referring to FIG. 3, a thread 21 representing attachment of media 24 tonet 26 is depicted. Thread 21 is one of a plurality of threadsconnection media 24 and net 26.

The depiction of rear wall 36 and inner wall surface 37 in FIG. 3 istypical of a view of sludge filter 10 attached to any wall, floor orsupport plate of container 30.

Referring to FIG. 4, a form of net 26 is depicted with the back surface79 up. A plurality of nodes 76 are defined at intersecting net members75. The indented sections 74 are defined by the net members 75intermediate nodes 76.

In the preferred embodiment sheets of net 26 and filter media 24 areattached. A preferred method of attachment comprises placing a sheet ofnet 26 adjacent a sheet of filter media 24 and sewing the net 26 andfilter media 24 together with sewn lines (partially represented bythread 21) extending around the perimeter of the sheets and, for largesheets, extending transversely at regular intervals. For appropriatesizes of net 26 and filter media 24, commercially available sewingmachines may be utilized to attach filter media 24 and net 26.Alternatively, filter media 24 and net 26 may be attached by staples,glue or a thermal bonding process. In a typical installation, thethickness of net 26 is less than 0.5 inches (˜1.25 cm) and the thicknessof filter media 24 is less than 0.4 inches (˜1.0 cm).

Referring to FIGS. 1, 3, 5, 6 and 7, in positioning sludge filter 10 incontainer 30, net 26 is intermediate filter media 24 and an innersurface 37 of container wall 36. In such position, sludge (not shown)introduced into container 30 will be disposed proximate surface 23 offilter media 24. Accordingly, sludge liquids will pass through filtermedia 24 under pressure of gravity and the mass of the sludge and sludgesolids (above a predetermined particle size) will not pass throughfilter media 24.

In a preferred embodiment, container 30 is provided with a drain cavity66 defined by rear wall 36, sidewalls 31, floor 32 and a cavity grate52. Cavity grate 52 is positioned within container 30, adjacent to floor32, and is constructed out of a sturdy perforated material resistant todeformation under the weight of a container full of sludge. In anexemplary embodiment cavity grate is formed from perforated metal.Preferably, drain cavity 66 is positioned at the lowest section ofcontainer 30. A drain 50 extends through sidewall 31. Drain 50 isconnectable to a drain line (not shown). The drain line typically isconnectable at drain 50 and includes a valve for controlled release ofsludge liquids for transmittal for disposal or further processing. Drain50 may be located in floor 32 or rear wall 36 as desired depending onthe orientation of the container 30.

Referring to FIG. 3, in the preferred embodiment, sludge filter 10 isremovably attached to container 30 by a two-part fastener system 28extending around the perimeter of the sludge filter 10. An exemplaryembodiment uses a hook and loop fastener system (e.g., a Velcro® typefastener—Velcro® is a registered trademark of Velcro Industries B.V.)for fastener system 28. A first fastener component 27 of the hook andloop fastener system is bonded to the interior surface 37 of container30. A second fastener component 29 is attached to filter media 24.

In an exemplary embodiment, the net 26 is sized with smaller lateraldimensions than the filter media 24 sheet leaving a peripheral segmentof filter media 24 extending around the sludge filter 10 outside net 26.The fastener component 29 is attached to the filter media 24 at suchperipheral segment. This allows the thickness around the perimeter ofthe sludge filter 10 to be the sum of the thickness of the filter media24, first fastener component 27 and second fastener component 29.

First fastener portion 27 is attached to the inner surfaces 37 ofcontainer 30 along the perimeter of container 30 onto which sludgefilter 10 is to be mounted. In the embodiment of FIGS. 1 and 2, thesections of container 30 onto which sludge filter 10 is to be mountedinclude rear wall 36, cavity grate 52, floor 32 and front wall 38.

In the case of sections of container 30 that are proximate to containertop 34, a protective bar 81 may be attached to container 30. Protectivebar 81 prevents sludge (not shown) from dislodging the upper edges ofsecond fastener component 29 from first fastener component 27.

Alternatively, the sludge filter 10 may be attached to the container 30by a plurality of retainer bars (not shown), such bars bolted, orotherwise fixed to said container. Alternatively, the sludge filter 10may be attached to the container 30 by a plurality of washers (notshown) held in place by screws or bolts (not shown). The use of retainerbars, bolts and washers is known in the art for attaching prior artfilters to a container 30, and may be readily adapted for use with thefilter 10 of the present invention.

Referring to FIGS. 1, 3 and 4, when sludge (not shown) is deposited incontainer 30, sludge is disposed against sludge filter 10 in contactwith filter media 24. Filter media 24 permits that passage of sludgeliquids, while impeding the passage of sludge solids (not shown) of apredetermined size based on perforation size in filter media 24. Sludgeliquids that pass through filter media 24 flow through perforations 42of net 26 and through the various openings defined by indented sections74 and rear wall surface 37. In like manner, sludge liquids would flowthrough channels 64 between indented sections 74 and the inner surface(not show) of front wall 38 and floor 32. As indented sections 74 allowvertical and horizontal flow intermediate rear surface 79 and inner rearwall surface 37, the liquids eventually gravity-flow downward to draincavity 66. In a net 26 having nodes 72 and indentations 70 of net frontsurface 77, liquids additionally flow through channels 62 intermediatenet front surface 77 and filter media 24.

In a preferred embodiment, sludge liquids are collected in drain cavity66. Drain 50 is selectively opened to permit the evacuation of sludgeliquids from drain cavity 66. Drain 50 is located in floor 32 in theembodiment of FIG. 1. Drain 50 may comprise a plurality of drains andmay be located, as appropriate in floor 32 or in a rear, side or frontwall of container 30 as appropriate.

After sludge liquids are separated from sludge solids, and sludge solidsare removed from container 30, sludge filter 10 may be removed fromcontainer 30 by separating first fastener component 27 and secondfastener component 29 of two-part fastener system 28 and pulling sludgefilter 10 from container 30. Sludge filter 10 may be cleaned, inspectedand repaired, then re-inserted into container 30 for subsequent use.

Referring now to FIG. 5, the sludge filter 10 of the present inventionis depicted in a typical rectangular container 130. Container 130includes a container floor 132, opposed sidewalls 131, a rear wall 136,and a front wall (not shown). The top container surface 134 is typicallyopen to receive sludge. A cover, not shown, may be provided which sealscontainer at top surface of 134.

Container 130 is provided with two drain cavities 166, each defined byrear wall 136, sidewalls 131, floor 132 and a cavity grate 152. Ifapplicable, an end (not shown) of each drain cavity 166 is defined by afront wall (not shown). In practice, the front wall of container 130comprises a gate that may be selectively opened. Accordingly, apartition (not shown) defines a front wall of the drain cavity 166.

Each cavity grate 152 is positioned within container 130 adjacent tofloor 132, and is constructed out of a sturdy perforated material.Preferably, each drain cavity 166 is positioned at the lowest section ofcontainer 130. A drain 150 extends through floor 132 at each draincavity 166. Each drain 150 may be connected to manifold line 151.Manifold drain line 151 is typically connected at drains 150 andincludes a valve 153 for controlled release of sludge liquids fortransmittal for disposal or further processing. Drains 150 may bealternatively located in sidewalls 131 or rear wall 136 as desired. Aplurality of drains 150 may be provided for each drain cavity 166. Aplurality of manifold drain lines 151 may be provided.

In the embodiment of FIG. 5, filter media 24 and net 26 are depictedarranged along sidewalls 131 and rear wall 136. Sludge liquids (notshown) migrate horizontally and vertically intermediate filter media 24and sidewalls 131 and rear wall 136 as previously described herein. Adrain cavity may be provided along rear wall 136. However, a draincavity is not required if the sludge filter 10 positioned on rear wall136 is in fluid communication with drain cavities 166. Alternatively,the sludge filter 10 may be disposed only along sidewalls 131.

As in the embodiment of FIGS. 1, 2 and 3, sludge filter 10 is removablyattached to container 130 by a two part fastener system 28 extendingaround the perimeter of the sludge filter 10 with first fastener portion27 of a hook and loop fastener system bonded to the interior surface ofcontainer 30 as a first fastener component 27 and the fastener component29 attached to filter media 24. A protective bar 81 is attached tocontainer 30 at the upper edge of sludge filter 10 to prevent sludge(not shown) from dislodging the upper edges of fastener component 29from first fastener component 27.

Referring now to FIG. 6, the sludge filter 10 of the present inventionis depicted in a typical rectangular container 130 together with acenter filter section 200. Container 130 includes a container floor 132,opposed sidewalls 131, a rear wall 136 and a front wall (not shown).Container 130 is provided with four drain cavities 166. The draincavities adjacent sidewalls 131 are each defined by rear wall 136,sidewalls 131, floor 132, a cavity grate 152 and a front wall (notshown) or partition (not shown) as described in relation to FIG. 5.

The center filter section 200 includes a vertical support plate 202.Support plate 202 extends vertically upward from floor 132. A sludgefilter 10 is attached to each side of support plate 202 in the manner ofattachment of sludge filter 10 to container 130 side walls 131 asdescribed in relation to FIGS. 1, 2 and 5. Accordingly, center filtersection 200 provides additional filter capacity within container 130.Drain cavities 166 of center filter section 200 are each defined by rearwall 136, support plate 202, floor 132, a cavity grate 152 and a frontwall (not shown) or partition (not shown). A plurality of apertures 204may be provided in support plate 202 to provide fluid communicationthrough support plate 202.

A drain 150 extends through floor 132 at each drain cavity 166. Eachdrain 150 may be connected to a manifold drain line 151. Each manifolddrain line 151 typically is connected at drain 150 and includes a valve153 for controlled release of sludge liquids for transmittal fordisposal or further processing. A plug (not shown) may be provided inlieu of valve 153. A plurality of drains 150 may be provided for eachdrain cavity 166. A plurality of manifold drain lines 151 maybeprovided.

In the embodiment of FIG. 6, sludge filter 10 is depicted arranged alongsidewalls 131 and support plate 202. Sludge liquids (not shown) migratehorizontally and vertically intermediate filter media 24 and sidewalls131 and intermediate filter media 24 and support plate 202 as previouslydescribed herein.

As in the embodiment of FIGS. 1, 2, 3 and 5, sludge filter 10 isremovably attached to container 130 by a two part fastener system 28extending around the perimeter of the sludge filter 10 with firstfastener portion 27 of a hook and loop fastener system bonded to theinterior surface of container 131 as a first fastener component 27 andthe fastener component 29 attached to filter media 24. A protective bar81 is attached to container 131 at the upper edge of sludge filter 10 toprevent sludge (not shown) from dislodging the upper edges of fastenercomponent 29 from first fastener component 27.

Referring to FIG. 7, sludge filter 10 is depicted arranged alongsidewalls 131. The embodiment of FIG. 7 does not include a support plateor a defined drain cavity 166. In the embodiment of FIG. 7, drains 150extend through floor 132 and sidewall 131 proximate floor 132. Eachdrain 150 may be connected to a manifold drain line 151. Each manifolddrain line 151 typically is connected at drain 150 and includes a valve153 for controlled release of sludge liquids for transmittal fordisposal or further processing. A plug (not shown) may be provided inlieu of valve 153. A plurality of drains 150 may be provided for eachdrain cavity 166. A plurality of manifold drain lines 151 may beprovided.

Sludge liquids (not shown) migrate horizontally and verticallyintermediate filter media 24 and sidewalls 131 and intermediate filtermedia 24 as previously described herein.

As in the embodiment of FIGS. 1, 2, 3 and 5, sludge filter 10 isremovably attached to container 130 by a two part fastener system 28extending around the perimeter of the sludge filter 10 with firstfastener portion 27 of a hook and loop fastener system bonded to theinterior surface of container 131 as a first fastener component 27 andthe fastener component 29 attached to filter media 24.

The foregoing disclosure and description of the invention isillustrative and explanatory thereof. Various changes in the details ofthe illustrated construction may be made within the scope of theappended claims without departing from the spirit of the invention. Thepresent invention should only be limited by the following claims andtheir legal equivalents.

1. A sludge container for separating sludge liquids from sludge solids,comprising: at least one container wall and a container floor; said atleast one container wall defining a container interior surface; a sludgefilter comprising a filter media and a filter net; said filter mediacomprising a planar sheet having a media front surface and a media rearsurface with transverse media openings extending from said media frontsurface to said media rear surface; said filter net comprising a planarnet having a net front surface and a net rear surface with transversenet perforations extending from said net front surface to said net rearsurface; said media openings liquid permeable; said media openingslimited to a predetermined size; said net perforations larger than saidmedia openings; said net rear surface comprising a plurality of rearsurface nodes and a plurality of rear surface indented sections; saidnet rear surface adjacent a container interior surface; a drain; saidnet perforations in fluid communication with said drain; a firstattachment component of a hook and loop fastener system extending arounda perimeter of said filter media; a second attachment component of ahook and loop fastener system attached to at least part of saidcontainer inner surface; and said first attachment component of a hookand loop fastener system alignable with said second attachment componentof a hook and loop fastener system.
 2. A sludge container according toclaim 1 further comprising: said net perforations, said plurality ofrear surface nodes and said plurality of rear surface indented sectionsdefining a plurality of flow channels intermediate said net rear surfaceand said container interior surface; and said flow channels allowinghorizontal and vertical fluid flow.
 3. A sludge container according toclaim 2 further comprising: said drain in fluid communication with saidflow channels.
 4. A sludge container according to claim 2 furthercomprising: said container having a drain cavity; said flow channels influid communication with said drain cavity; and said drain in fluidcommunication with said drain cavity.
 5. A sludge container according toclaim 1 further comprising: said net front surface comprising aplurality of front surface nodes and a plurality of front surfaceindented sections; said net perforations, said plurality of frontsurface nodes and said plurality of front surface indented sectionsdefining a plurality of front flow channels intermediate said net frontsurface and said media rear surface.
 6. A sludge container according toclaim 5 further comprising: said drain in fluid communication with saidfront flow channels.
 7. A sludge container according to claim 5 furthercomprising: said container having at least one drain cavity; said frontflow channels in fluid communication with said at least one draincavity; and said drain in fluid communication with said at least onedrain cavity.
 8. A sludge container according to claim 7 furthercomprising: said sludge filter selectively attachable to and removablefrom said container interior surface.
 9. A sludge container according toclaim 5 further comprising: said sludge filter selectively attachable toand removable from said container interior surface.
 10. A sludgecontainer according to claim 1 further comprising: said filter mediasewn to said net.
 11. A sludge container for separating sludge liquidsfrom sludge solids, comprising: at least one container wall and acontainer floor; said at least one container wall defining a containerinterior surface; a sludge filter comprising a filter media and a filternet; said filter media comprising a liquid-permeable planar sheet havingmedia openings; said filter net comprising a planar net having a netfront surface and a net rear surface with transverse net perforations;said filter net comprising a plurality of nodes and a plurality ofsurface indented sections; at least one drain; said net perforations influid communication with said at least one drain; a first attachmentcomponent of a hook and loop fastener system extending around aperimeter of said filter media; a second attachment component of a hookand loop fastener system attached to at least part of said containerinner surface; and said first attachment component of a hook and loopfastener system alignable with said second attachment component of ahook and loop fastener system.
 12. A sludge container according to claim11 further comprising: said container having at least one drain cavity;said net perforations in fluid communication with said at least onedrain cavity; and said drain in fluid communication with said at leastone drain cavity.
 13. A sludge container according to claim 11 furthercomprising: said sludge filter selectively attachable to and removablefrom at least a portion of said container interior surface.